Why Aquaponics?

Why Not Hydroponics? It’s all about sustainability off the grid. While sharing many similarities, Aquaponics is 100% organic and can be completely self-sustaining, unlike hydroponics, which depends on added nutrients. Let’s look at the basic differences.

Hydroponics vs Aquaponics

With hydroponics, plant nutrients in the form of mineral salts are added to the water that feeds the plant roots. This is exactly analogous to the mineral salts in ordinary soil being dissolved by rain or irrigation water so they can be absorbed by the plant roots. In other words, the plants in hydroponic agriculture feed on the same mineral salts that plants in the ground feed on, except in hydroponic agriculture the salts are fed by adding them in measured amounts to the water that circulates in the hydroponic system. This is all well and good, except food production depends on the availability of the mineral salts, generally obtained from hydroponic supply stores. If you can’t get to a store, you can’t buy the mineral salts. That is obviously a problem for hydroponics in terms of sustainability off the grid.

Aquaponics differs in that the mineral salts plants feed on – and all plants feed on the same mineral salts, no matter how they are obtained – are provided by nitrogen-fixing bacteria in the aquaponic water solution. These nitrogen-fixing bacteria turn organic matter into mineral salts in the same way they do in ordinary agriculture, especially including organic agriculture where the conversion takes place in the soil. It’s important to understand that organic agriculture does not consist in feeding organic matter to plants. The plants simply cannot absorb organic matter directly! It must be converted into the mineral salts plants use for food. Nitrogen-fixing bacteria do this job regardless of the agriculture system employed, except for hydroponics, in which measured mineral salts in liquid chemical form are added to the water by the grower. Therefore, hydroponic agriculture is not organic agriculture!

aquaponic cycle

In traditional organic agriculture, some form of compost is the organic matter converted in the soil by the nitrogen-fixing bacteria into mineral salts for the plants. In aquaponics, the organic matter converted by the nitrogen-fixing bacteria in the water is fish waste. Therefore, fish are an essential component of aquaponics. Of course, the fish need something to eat so they can live and produce the necessary fish waste for conversion to mineral salts. The fish food is typically worms and worm castings, which is essentially worm waste, and probably the richest compost there is. Worms make a natural choice for the first stage of aquaponics because they are easy to raise and manage, reproduce easily on their own, and produce plenty of nutrient-rich compost. In a suitably designed aquaponic system, no store-bought components are required.

It is true that the aquaponic water solution must be circulated from the fish to the plants, and optionally to a shellfish stage for final filtering of the water, and then back to the fish. And it is true that such circulation is most easily achieved using pumps that run electrically, but it is also true that the electricity requirement is quite low and can be supplied economically by on-site power production systems, such as solar, wind or other. If your property includes a running stream, this can be utilized for hydro-power production. Even a small stream can supply more than enough power to run an aquaponic system. Watch for upcoming articles on power production.